The present invention relates generally to the field of ink jet printers, and more particularly, to ink delivery systems for pen designs.
Many conventional ink jet printers use an integrated print head and ink supply configuration in a single ink jet cartridge. One such exemplary integrated cartridge is the tri-color Hp cartridge 51625A, for use in the Hp Deskjet 560 printer. In the Hp Deskjet 560 printer, a cartridge is replaced whenever an ink supply is exhausted. Replacing the entire cartridge, however, is relatively expensive, as the print head adds substantial cost to the integrated cartridge even though it often does not need to be replaced every time the ink supply is spent.
Some conventional ink jet printers have been developed with a separated print head and ink supply configuration to reduce the cost of replacement cartridges. These configurations are typically described as having a semi-permanent and reusable xe2x80x9cpen bodyxe2x80x9d and print head mechanism supplied with ink from a remote, off-axis (or off-board) ink reservoir (i.e., ink supply). Exemplary systems are described in U.S. Pat. No. 5,757,406 (xe2x80x9cNegative pressure ink delivery systemxe2x80x9d) and U.S. Pat. No. 5,886,718 (xe2x80x9cInk-jet off axis ink delivery systemxe2x80x9d). In such systems, an individual ink supply for the printer (e.g., a magenta ink container) is replaced or refilled whenever that particular ink supply is exhausted. Replacing individual ink supplies correspondingly reduces the recurring costs by eliminating the need to replace the print head along with the ink supply every time an ink supply is spent. Separated print head and ink supply configurations, however, still suffer from many problems.
Conventional ink jet pens (including both integrated and separated print head/ink supply configurations) are typically made of an amorphous material (e.g., various plastics), to reduce the materials cost of the print head. Depending on the particular pen configuration and material used, however, residual ink within the pen undergoes water evaporation over time, especially during lulls between print jobs which can last for several days (e.g., over a weekend). As water slowly evaporates from the ink, the ink properties (e.g., viscosity, color tone, etc.) change, thereby degrading the ink quality and correspondingly, the printer performance on subsequent print jobs.
Unlike large conventional xe2x80x9cbookshelfxe2x80x9d printers, many new printer applications involve relatively small printers (e.g., digital camera printers, palmtop printers, calculator printers, laptop printers, etc.). One such printer is the Hp Photosmart 100, which is approximately 218xc3x97108xc3x97115 mm. These printers are designed to print on media generally less than about 100 mm in width.
Some problems suffered by conventional printers, such as water evaporation, are amplified in small printers (in comparison to standard xe2x80x9cbook shelfxe2x80x9d printers), because the size of the print head and ink supply components shrink corresponding to the overall reduced printer size. By way of example, a 100 cc ink supply (e.g., a xe2x80x9cbook shelfxe2x80x9d printer ink supply) suffering from a 1 cc loss in water due to evaporation still has 99 cc of ink at a {fraction (99/100)} (i.e., 99%) purity. In contrast, a 10 cc ink supply (e.g., a small printer) suffering from a 1 cc loss in water due to evaporation has only 9 cc of ink at a {fraction (9/10)} (i.e., 90%) purity, a 9% greater reduction in purity than that of the 100 cc ink supply. Hence, as the printer size shrinks, the water loss problem is substantially increased, which leads to greater problems in degraded ink properties and printer performance.
Furthermore, as water evaporates from a printer, it is generally exchanged with air. Air pockets and/or air bubbles can form in the ink supply, along ink conduits between the ink supply and the print head, or even within the print head itself in areas such as ink cavities behind each ink jet nozzle. With smaller printers, these air pockets and/or air bubbles lead to significant printing inconsistencies, such as varying pressure within the system, interrupted ink delivery from the ink supply to the print head, and other such problems.
Thus, a need exists for an improved ink delivery system, and in particular, for an improved ink delivery system for miniature pen designs.
According to one embodiment of the present invention, an ink delivery device is provided for supplying ink via an ink conduit from an ink supply to a print head attached to a manifold, the manifold adapted to route ink into the print head and back to the ink conduit for routing to the ink supply. The ink delivery device comprises a pressure controller operating on the ink conduit between the print head and the ink supply, the pressure controller including a sealing device adapted to seal off the ink conduit and a cap adapted to selectably expose the pressure controller to ambient conditions. The pressure controller is adapted to purge the print head of ink between print jobs.
According to another embodiment of the present invention, a method of delivering ink to an ink applicator system including an ink applicator is provided comprising the steps of priming the ink applicator prior to printing, and purging the system after printing to remove ink from the ink applicator system, wherein the backpressure within the ink applicator system is maintained below a predetermined maximum during the priming and purging steps.
According to another embodiment of the present invention, an ink delivery system is provided for supplying ink from an ink supply to a print head via an ink conduit. The system comprises means for priming the print head, means for purging the print head after printing, and means for maintaining backpressure within the system below a predetermined maximum.
According to another embodiment of the present invention, an inkjet printer is provided comprising a print head, the print head having a total ink volume capacity of less than about 0.05 cc""s per color, and
a manifold adapted to route ink into the print head and out to an ink supply via an ink conduit.